Place the shallot in a small bowl with the sumac, vinegar and ½ teaspoon of salt. Use your hands to mix together - you want the sumac to really be massaged into the shallots - then set aside for 30 minutes, to soften.
Slice the large tomatoes in half lengthways and then into 1-1 ½cm wedges and place in a large bowl. Slice the cherry tomatoes in half lengthways and add to the bowl. Pour in the olive oil and mix gently with the basil leaves, ⅓ teaspoon of salt and a generous grind of pepper.
Arrange the tomatoes on a large platter and spread over the shallots, pulling some of the tomatoes and basil above the shallots. Sprinkle with the pine nuts and serve.
